article · Molecular Plant
A novel circular single-stranded DNA virus, named Diaporthe sojae circular DNA virus 1 (DsCDV1), has been discovered in the plant pathogenic fungus Diaporthe sojae isolated from pear trees. The virus possesses an evolutionary linkage to both the Geminiviridae and Genomoviridae families, prompting the proposal of a new viral family termed Gegemycoviridae. When introduced into its fungal host, DsCDV1 significantly reduces fungal growth and almost completely abolishes virulence. Furthermore, the virus can systematically infect pear and tobacco seedlings, where it confers broad-spectrum resistance against fungal diseases. Investigation of viral proteins indicates that the P3 protein acts as a movement protein, localising to plasmodesmata and enabling systemic viral transport in plants. These characteristics reveal an evolutionary bridge between plant and fungal single-stranded DNA viruses with notable biological properties.
Fungal pathogens cause severe damage to agricultural crops and are often difficult to control. Discovering a single-stranded DNA virus that simultaneously disarms a harmful fungus and protects host plants against broader fungal infections provides a valuable mechanism for crop protection. It also uncovers an important evolutionary connection between viruses that infect plants and those that infect fungi.
This research could support the development of biological control agents for managing destructive fungal diseases in crops such as fruit trees. Potential users include agricultural biotechnology developers and crop protection organisations. Because the findings are based on laboratory transfection and seedling infection trials, the technology is at an early experimental stage and will require extensive field testing and safety assessments before any commercial deployment.
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Circular single-stranded DNA (ssDNA) viruses have been rarely found in fungi, and the evolutionary and ecological relationships among ssDNA viruses infecting fungi and other organisms remain unclear. In this study, a novel circular ssDNA virus, tentatively named Diaporthe sojae circular DNA virus 1 (DsCDV1), was identified in the phytopathogenic fungus Diaporthe sojae isolated from pear trees. DsCDV1 has a monopartite genome (3185 nt in size) encapsidated in isometric virions (21-26 nm in diameter). The genome comprises seven putative open reading frames encoding a discrete replicase (Rep) split by an intergenic region, a putative capsid protein (CP), several proteins of unknown function (P1-P4), and a long intergenic region. Notably, the two split parts of DsCDV1 Rep share high identities with the Reps of Geminiviridae and Genomoviridae, respectively, indicating an evolutionary linkage with both families. Phylogenetic analysis based on Rep or CP sequences placed DsCDV1 in a unique cluster, supporting the establishment of a new family, tentatively named Gegemycoviridae, intermediate to both families. DsCDV1 significantly attenuates fungal growth and nearly erases fungal virulence when transfected into the host fungus. Remarkably, DsCDV1 can systematically infect tobacco and pear seedlings, providing broad-spectrum resistance to fungal diseases. Subcellular localization analysis revealed that DsCDV1 P3 is systematically localized in the plasmodesmata, while its expression in trans-complementation experiments could restore systematic infection of a movement-deficient plant virus, suggesting that P3 is a movement protein. DsCDV1 exhibits unique molecular and biological traits not observed in other ssDNA viruses, serving as a link between fungal and plant ssDNA viruses and presenting an evolutionary connection between ssDNA viruses and fungi. These findings contribute to expanding our understanding of ssDNA virus diversity and evolution, offering potential biocontrol applications for managing crucial plant diseases.
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DOI: 10.1016/j.molp.2024.05.003
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